Application of colon cancer screening has not kept pace with evidence supporting its value. This R-21 proposal will set the stage for long term, ongoing exploration of colon cancer screening practices through colonoscopy by creating the infrastructure for a population-based colonoscopy registry and beginning to enroll patients. The registry is modeled on population-based mammography registry based in the New Hampshire Mammography Network, which is part of a national mammography consortium. Building on this work in New Hampshire, we will begin to develop a primary care colon cancer screening consortium. The consortium will create initial linkages between practice-based research networks in New Hampshire and New York City as part of a long term effort to enhance knowledge and quality of colon cancer screening in primary care with an emphasis on addressing health care disparities in colon cancer screening. Specific aims of this proposal are: 1. To develop the infrastructure and procedures needed for a population-based colonoscopy registry in New Hampshire; 2. To enroll in the registry initial patients receiving colonoscopy through Dartmouth Hitchcock Medical Center and its 12 primary care practices; 3. To assess the feasibility and pilot test expanding the registry to include all colonoscopies performed on New Hampshire residents; 4. To explore the feasibility of and take initial steps towards developing a population-based colonoscopy registry in New York City focused on under served populations receiving primary care through community health centers. This will provide initial steps to create a primary care colon cancer screening consortium. The Dartmouth-based research team brings years of experience with research in primary care, multi-site National Cancer Institute-sponsored clinical trials, and experience with the NH Mammography Network to this developmental project. The project is backed by the resources of Norris Cotton Cancer Center, the endorsement of the New Hampshire Governors Advisory Council on Cancer and Chronic Disease, and by the commitment of primary care clinicians and colonoscopists state-wide. The consortium partner has well-established relationships with the Dartmouth team bringing substantial patient racial and economic diversity to the effort.